The invention relates to a detector for detection of ionizing radiation, and to an apparatus for use in planar beam radiography.
A detector and an apparatus of the kind mentioned above are described in the copending U.S. application Ser. No. 08/969,554 and the copending SE applications SE 9901326-0, SE 9901327-8, SE 9901325-2 and SE 9901562-0, which are incorporated herein by reference. The detector described therein includes a gaseous parallel plate avalanche chamber. The detector provides good resolution, high X-ray detection efficiency, and possibility to count every photon incident in the detector. This provides a huge number of possibilities when processing the detection signals, such as energy detection, discriminating detection signals from photons in certain energy ranges or from photons incident at certain distance ranges from the anode or the cathode.
When using a detector of this kind in planar beam X-ray radiography, e.g. slit or scan radiography, an apparatus which provides that an object to be imaged only needs to be irradiated with a low dose of X-ray photons is achieved, while an image of high quality is obtained.
For gaseous parallel plate avalanche chamber it has been regarded as necessary that the anode and cathode plates are parallel, and much effort has been made to achieve high parallelism between the plates. Such a detector is a one-dimensional detector, and to obtain a two-dimensional image the second dimension for the image can be achieved by scanning the X-ray beam and detector across the object to be imaged. To ease the X-ray tube loading and simplify the mechanics (by reducing the scanning distance), a multiline set of one-dimensional detectors is beneficial. This also shortens the scanning time.
For such a multiline detector a number of one-dimensional detectors can be stacked. In such a case it is desirable that the detectors are aligned with the X-ray source. When the plates of the detector are parallel, the assembling and alignment of a detector unit, comprised of a plurality of one-dimensional detectors, is complicated and time-consuming.
The present invention is directed to a one-dimensional detector for detection of ionizing radiation, which employs avalanche amplification, and can be stacked with other one-dimensional detectors to form a detector unit in a simple and cost effective way.
This and other objects are attained by a detector for detection of ionizing radiation, comprising a chamber filled with an ionizable gas, first and second electrode arrangements provided in said chamber with a space between them, said space including a conversion volume, and an electron avalanche amplification unit arranged in said chamber, and wherein the first and second electrode arrangements exhibit a first and a second main plane, said planes being non-parallel, said electron avalanche amplification unit including at least one avalanche cathode arrangement and at least one avalanche anode arrangement, wherein an electric field for avalanche amplification is created between said at least one avalanche cathode arrangement and said at least one avalanche anode arrangement. The above detector provides good resolution, high X-ray detection efficiency, and the ability to count every photon incident in the detector.
The above detector also provides good energy resolution for X-rays.
The above detector also can operate at high X-ray fluxes without performance degradation and has a long lifetime.
The above detector also provides effective detection of any kind of radiation, including electromagnetic radiation as well as incident particles, including elementary particles.
The present invention is also directed to an apparatus for use in planar beam radiography, comprising at least one one-dimensional detector for detection of ionizing radiation, which employs avalanche amplification, and can be stacked with other one-dimensional detectors to form a detector unit in a simple and cost effective way.
This and other objects are attained by an apparatus for use in planar beam radiography, comprising an X-ray source, a substantially planar beam unit for forming a substantially planar X-ray beam positioned between said X-ray source and an object to be imaged, a chamber filled with an ionizable gas, first and second electrode arrangements provided in said chamber with a space between them, said space including a conversion volume, and an electron avalanche amplification unit arranged in said chamber, and wherein the first and second electrode arrangements exhibit a first and a second main plane, said planes being non-parallel, said electron avalanche amplification unit including at least one avalanche cathode arrangement and at least one avalanche anode arrangement, wherein an electric field for avalanche amplification is created between said at least one avalanche cathode arrangement and said at least one avalanche anode arrangement.
The above apparatus can also be used in planar beam radiography, e.g. slit or scan radiography,where the object to be imaged only needs to be irradiated with a low dose of X-ray photons, but an image of high quality is still obtained.
The above apparatus also can be used in planar beam radiography, in which a major fraction of the X-ray photons incident on the detector can be detected, for further counting or integration in order to achieve a value for each pixel of the image.
The above apparatus can also be used in planar beam radiography, in which image noise caused by radiation scattered in an object to be examined is strongly reduced.
The above apparatus can also be used in planar beam radiography, in which image noise caused by the spread of X-ray energy spectrum is reduced.
The above apparatus can also be used in planar beam radiography, including the simple and inexpensive detector that can operate with high X-ray detection efficiency and with good energy resolution for X-rays.
The above apparatus can also be used in planar beam radiography, including the detector which can operate at high X-ray fluxes without a performance degradation and has a long lifetime.